The production of electro-optical devices such as LiNbO.sub.3 substrates supporting titanium-diffused waveguides with minimal optical losses is a desired goal in the electro-optical field. More specifically, it is highly desirable to provide such optical waveguides that can be proficiently manufactured with superior adhesion of substrate coatings and electrodes without deteriorating the transmission characteristics of the optical waveguides.
The desirability of providing improved manufacturing processes for producing optical waveguides in an economical manner is well appreciated in the prior art. The advantage of optical waveguides and their integration in electro-optical devices is well known, and has become even more significant in the miniaturization of various electro-optical devices. Such systems are described, e.g., by S. E. Miller in "Integrated Optics: An Introduction," Bell System Technical Journal, Vol. 48 (1969), pp. 2059-2069, and they can be manufactured by techniques such as described by E. G. Spencer et al., "Ion Beam Techniques for Device Fabrication," Journal of Vacuum Science and Technology, Vol. 8 (1972), pp. 552-570. The prior art has further recognized the advantages of utilizing lithium niobate (LiNbO.sub.3) substrates having diffused titanium waveguides developed adjacent their surfaces. The ability to provide various switching arrangements by depositing electrode material across the waveguides has also been appreciated in the prior art, such as U.S. Pat. No. 4,184,738. The optimum production of these electro-optical devices is still a significant challenge to the prior art.
Lithium niobate substrates are generally cleaned by solvents and blown dry with nitrogen. Chemical cleaning, however, has the capacity of leaving trace contaminants of chemicals on the surface of the substrate. Even if the substrates were properly cleaned by chemicals, there was still the possibility of contamination by the transporting of the substrates to the deposition site. The prior art was also aware of the ability to pre-etch a substrate with argon ions preparatory for the depositing of a layer of material on the substrate. This pre-etching step, however, could not be utilized with a lithium niobate substrate having developed optical waveguides, because it would damage the transmission capacities of the waveguides.
Thus, the prior art is still seeking improvements in the manufacturing of lithium niobate substrates with optical waveguides and improved electro-optical devices with minimal throughput loss.